A project on lesson study carried out in 2006 and 2007 aimed to find out how it can be used to bring about enhanced teacher learning and instructional improvements. This two-year intensive collaboration between researchers and a local primary school involved planning, teaching and observing research lessons together, as well as studying the processes of school-based curriculum development and teacher learning. The challenges of implementing lesson study in the Singapore context and its evolving local adaptations were carefully documented and analysed. We found that with strong school support, lesson study could bring about continual instructional improvement and a sense of community among the teachers, even though its time-consuming nature may pose numerous challenges for the teachers and schools.